Motor fuel



United States Patent C) cc MOTOR FUEL John P. Pellegrini, Jr., Blawnox,and Helen I. Thayer,

Pittsburgh, Pa., assignors to Gulf Research & Development Company,Pittsburgh, Pa., aco'rporatiori of Delaware No Drawing. ApplicationNovember 27, 1953 Serial No. 394,871

5 Claims. (Cl. 4469)' at high compression ratios, it has generally beennecessary to employ a fuel having a high octane number. To obtain a highoctane number most fuels require'the addi tion of an anti-knock agentsuch as tetraethyl lead. While the addition of tetraethyl lead togasoline improves its octane number, the resulting fuel has" certaindisadvantages arising from the presence of the lead. One of the chiefobjections to the use of leaded-fuels arises from the tendency of thefuel upon being burned to form lead deposits on the walls of thecombustion chamber of-the engine and on the terminals of; the sparkplugs, thus reducing the efficiency of the engine. The net effect ofthese deposits 'is that the octane number requirement of the enginegradually increases as the engine is operated until someequilibriumoctane requirement is reached. The equilibriumoctane number requirementof some engines which have been in operation for 100 or more hours maybe 50 to 60 percent higher than the octane number requirement of'thesame engines at the start of their operation.

In an attempt to overcome the detrimental effect of the lead deposits inan engine, various scavenging agents have been added to the fuel tochange the form of the lead deposit to-one which is'less-detrimentalrFor example,-various volatile alkyl halides such as ethylene dibromideand/or ethylene dichloride have been used withthe' result that the leaddeposits have :com'prised the bromides of lead is frequently evidencedby' engine knocking. The knocking thus encountered isthatre sulting fromthe initiation of a flame front at anypoint in the fuel-air mixtureprior to the regularly-timed spark ignition. knocking due to explosiveautoignition ofthe unburned portion of the fuel-air mixture to betraversed by the normal flame from the spark plug.

We have discovered that a motor fuel and particularly leaded-gasolinecanbe improved with respect to its tendenc'y to preignite in anengineand that the octanenumber requirement of an engine in which his used can'be lowered by incorporating in the fuel a small amount of anorgano-phosphoramide having the following structural formula:

The adverse effect encountered asa result of the deposits of thechl'orides and This knocking should not be confused with 2,863,743Patented Dec. 29, 1958 Ind where R is a substituent selected from theclass consisting of an alkyl group and hydrogen. Specific examples ofthe alkyl radicals which we intend to include are methyl; ethyl; propyl;isopropyl; butyl; sec-butyl; amyl; hexyl; heptyl; octyl; nonyl; decyl;undecyl; dodecyl; tridecyl; tetradecyl; pentadecyl; hexadecyl;heptadecyl; octadecyl; and the like. I

While all the compounds designated by the above structural formula canbe used to produce a motor fuel having improved preignitioncharacteristics, it. will be understood, of course, that theireffectiveness may vary.

The alkyl-phosphoramides are particularly advantageous for use in themotor fuels of our invention. While compounds wherein the R group is along-chain alkyl radical such as octyl, nonyl, decyl, octadecyl, and thelike can be employed, we prefer, for economic reasons, to use thosealkyl-phosphoramides wherein the alkyl group contains from 1 to 4 carbonatoms; For example, we prefer to employ the methyl, ethyl, propyl andbutyl phosphoramides. Hexamethylphosphoram'ide has been found to beparticularly elfective'in reducing the preignition'characteristics of agasoline normally tending to preignite in 'the combustion chamber of aspark-ignition engine.

Hexamethylpho-sphoramide hasalso been found to be effective in reducingthe octane number requirement of an engine.

Specific examples of other compounds comingwithin the above structuralformula and which can be used to produce an improved motor fuel areN,N,N"-trimethylphospho-ramide; N,N,N"-triethylphosphoramide; N,N,N'-triisopropylphosphoramide; and N,N',N"-trime'thyl-N,N',N"-tributylphosphoramide.

While any single organo-phosphoramide can be used in'c'onjunction with amotor fuel to produce the improved fuels of our invention; it should beunderstood that mixtures of two or more organo-phosphoramides'canbeused.For example, a mixture of trimethylphosphorarnideandhexamethylphosphor'amide can be used instead of either one of thesecompounds alone. Therefore, when the term organo-phosphoramide isus'edhereiii and 'in'the appended claims, it will be understood that'oneor more organo-phosphoramides is intended. g,

The amount of the organo-pho'sphoramide 'which is incorporated in thefuel depends 'to" some extent upon the'particular fuel employed, aswellas the particular organo-phosphoramide selected. In general, the amountis based upon that amount theoretically required toconv ert the leadintroduced-into the fuel in the form of tetraethyl lead to leadorthophosphate. While improved resnlts'can be obtained with verysmall'amounts, amounts corresponding to at least about 0.1 times thattheoretically required are preferred. Especially good results areobtained by the use of at least about 0.2 times the theoretical amountrequired. In generaL'itis notnecessaryto employ more. than 1.5 times theamount theoretically required. Amounts greater than 1.5 times thetheoretical amount can be employed, but for economic reasons, We preferto use only the amount required to give the desired improvement.Therefore, we prefer to employ an amount equal to about 0.2 to about 1.5times that theoretically required to convert the' lead to leadorthophosphate. In view of the fact that the amount of tetraethyl leadin the gasoline varies from one fuel to another, it is difficult tostate on a weight basisthe amount of organo-phosphoramide based upon theWeight of gasoline. However, once knowing the amount of tetraethyl leadpresent in the gasoline, it is an easy matter to calculate the amount ofthe organo-phosphoramide required. Most gasolines on the market todaycontain up to about three cubic centimeters of tetraethyl lead pergallon of gasoline. Based upon fuels containing up to about three cubiccentimeters of tetraethyl lead per gal- Ion of gasoline, we havedetermined that the amount of organo-phosphoramide required inaccordance with our is that the molecular weight of one compound may betwice the molecular weight of another compound, so that to get anequivalent amount of phosphorus when using the compound having thegreater molecular weight, one is required to use twicethe amount ofcompound on a weight basis. In any event, the amount oforgano-phosphoramide used is sufficient to inhibit or substantiallyprevent preignitionof a gasoline normally tending to preignite in thecombustion chamber of an engine.

The motor fuel to which the organo-phosphoramide is added can comprise amixture of hydrocarbons boiling in the gasoline boiling range. Forinstance, the gasoline employed can be either a straight-run gasoline ora gasoline obtained from a conventional cracking process, or mixturesthereof. The gasoline to which the organophosphoramide is added inaccordance with our invention can also contain components obtained fromprocesses other than cracking, such as alkylation, isomerization,hydrogenation, polymerization, hydrodesulfurization, hydroforming,Platforming, or combinations of two or more of such processes, as wellas synthetic gasoline obtained from the Fischer-Tropsch and relatedprocesses.

In addition to the organo-phosphoramide, the motor fuel can containother additive agents including oxidation inhibitors, anti-rust,anti-knock and anti-freeze agents, metal deactivators, dyes, and thelike. When the anti-knock agent is an organo-metallic composition suchas tetraethyl lead, the motor fuel may also contain a lead scavengingagent such as a volatile alkyl halide or a mixture of volatile alkylhalides such as ethylene dichloride and/ or ethylene dibromide. Whenthese halides are used they are ordinarily present in an amountcorresponding to about one or two cubic centimeters per gallon ofgasoline. As the amount of tetraethyl lead used goes down, however, thelead scavenging agent required also decreases. In accordance with ourinvention, the organo-phosphoramide can replace in whole or in part thevolatile alkyl halide lead scavenging agent. However, theorgano-phosphoramide can be used in conjunction with the usual amount ofvolatile alkyl halide without deleteriously affecting the beneficialeffects of the organo-phosphoramide.

The organo-phosphoramides present no particular problem when it comes toadding them to the gasoline. While the organo-phosphoramide can be addeddirectly to the gasoline, one convenient method of adding it to the fuelis by forming a concentrate thereof, thereafter adding the concentrateto the fuel. Thus, a gasoline-benefiting concentrate can be formed byadmixing an organo-metallic anti-knock composition with anorgano-phosphoramide. In some instances, it may be desirable to employ amutual solvent. Any solvent which does not adversely affect thedesirable properties of the fuel can be used. The concentrate can, ofcourse, contain other additive agents such as an oxidation inhibitor, ananti-rust agent, an antiknock agent, an anti-freeze agent, a metaldeactivator, a scavenging agent and a dye. When the anti-knock agent isan organo-metallic composition, such as tetraethyl lead, the scavengingagent can comprise a mixture of ethylene dibromide and ethylenedichloride. Since the amount of organo-phosphoramide required depends tosome extent upon the amount of the organo-metallic anti-knockcomposition, this-method of adding the organo-phosphoramide to thegasoline serves as a convenient way of adding the correct amount. Thus,a

son for this is that the effectiveness of the compounds varies from onecompound to another. Another reason gasoline-benefiting concentrate canbe made by admixing tetraethyl lead with an alkyl-phosphoramide whereinthe alkyl-phosphoramide is present in an amount between about 0.1 and1.5 times the theoretical amount required to convert the lead to leadphosphate.

In order to illustrate the decrease in octane number requirement for anengine when operating with an improved gasoline in accordance with thisinvention, octane rating tests were made in a single-cylinder engine.The engine installation used was a modification of the standard ASTMassembly as described in the laboratory knockrating test procedure CRCdesignation F-1-545 and CRC designation F2545. These tests are describedin the CRC Handbook, 1946 edition, compiled by the Coordinating ResearchCouncil, Incorporated. The engine assembly was modified to the extentthat the Waukesha CFR engine was equipped with an L-head cylinderinstead of an overhead valve.

The engine was operated on a cycling schedule alternating between thefollowing conditions:

AirzFuel Ratio Ignition Timing Coolant Temperature, "F Oil Temperature,"F Carburetor, Intake Air, Humidity Control :1:5: Ice Tower... IceTower.

1 TDC=Top Dead Center.

In carrying out these tests, octane number requirements were recorded atthe beginning of each test when the engine was clean and thenperiodically until the octane requirement had reached an equilibriumpoint. Table I sets forth the data obtained when the engine was operatedwith a reference gasoline containing about three cubic centimeters oftetraethyl lead per gallon of gasoline and the same leaded-gasolinecontaining 1.5 grams of hexamethylphosphoramide per gallon of gasoline.The amount of hexamethylphosphoramide employed corresponded to about0.73 times that theoretically required to react with all of the leadpresent to form lead phosphate. In each case, the gasoline alsocontained a small amount of an antioxidant, a metal deactivator, a leadscavenging agent, and a dye.

Table I Engine Octane Requirement 1 Reference Gasoline 1 Researchmethod.

The above data show that the equilibrium octane re- -quirement of asingle cylinder CFR engine employed in the test was about 88whenoperating with the reference gasoline and about 68 when operatingwith the reference gasoline containing 1.5 grams ofhexamethylphosphoramide per gallon of gasoline. Thus, the equilibriumoctane requirement of the engine operating with the improved gasolinewas about 20 numbers below the requirement of the same engine operatingwith unimproved gasoline. Table II gives the inspection data on thegasolines used in the engine octane number requirement test.

In order toIillu'strate the improved results with respect topreignition,'.a;test-waswemployedin which the fuel was burned in astationary Cadillacv engine having a 9:1 compression'ratio. The'en'gineconditions'at the time of the preignition evaluation'we're"as'follows:

, Speed 1,000 and 2,000 R..P. M.

"Spark advance 10.

AirzFuel ratio 111521 and 10.3:1 at 21,000 and 2,000-R. P.

M., respectively.

In this test the load and throttle position are varied, dependent uponwhen preignition is encountered. At the start of the test the engine isunder no load. The throttle is gradually increased until preignition isobserved. If full throttle is reached without preignition, the engine isoperated at full throttle for 30 seconds or less if preignition occurssooner. If preignition is not encountered after 120 hours (5 days), thetest is usually discontinued. The data set forth in Table III wasobtained when the Cadillac engine was operated under the above test procedure with a reference gasoline normally tending to preignitecontaining about 1.5 cubic centimeters of tetraethyl lead per gallon ofgasoline and the same leadedgasoline containing 1.0 (1.1 times thetheory) gram of hexamethylphosphoramide per gallon of gasoline. In eachinstance, the gasoline also contained a small amount of an antioxidant,a metal deactivator, and a lead scavenging agent.

It will be noted from the data in Table III that the engine operating onthe reference gasoline showed mild preignition Within 48 hours and thatviolent preignition occurred within 72 hours. When the same engine wasoperated with the improved gasoline of the invention, there was nopreignition even after 100 hours of operation. After 120 hours ofoperation with the improved fuel, only mild preignition was observed.

Table IV gives the inspection data on the gasolines employed in thepreignition test.

Upon examination of the engine after operation with the referencegasoline and the reference gasoline containing hexamethylphosphoramide,it was observed that the engine deposits were dissimilar in manyrespects.

The engine deposits resulting from .using the reference igasolinewereIbrownish-bla ck in color,.had a tendency to adhere to metalsurfaces and, when scrapedlfrom metal csurfaces were .inclinedto peeloff in the form of flakes.

The engine deposits resultingffrom using the reference gasolinecontaining hexamethylphosphoramide, however, were light-colored,powdery, and were removed from the metal surfaces vupon which theyhadbeen deposited with :llittle :difliculty.

In each of the preignition testsdescribedabove, when usingthezreference,gasolineand the samegasoline con-.taininghexamethylphosphoramide, the combustion cham- .bers and .spark.plugs of thezCadillac engineat the st-art .ofrthetest weresubstantially free from deposits giving rise to preignition. In order toillustrate the effect of the improved motor fuel of the invention on anengine in which preignition has already commenced, the above test wasrepeated with the exception that when deposit-induced preignition wasencountered when using the reference gasoline, the fuel was changed tothe gasoline containing hexarnethylphosphoramide without shutting downthe engine. Thus, when violent preignition was encountered with thereference gasoline at 72 hours, the fuel supply was switched to the samegasoline containing 1.0 gram of hexamethylphosphoramide. While theviolent preignition did not subside immediately, probably because of thedeleterious deposits laid down by the reference gasoline, there was agradual improvement. For instance, at the end of 16 hours of operationwith the fuel containing hexamethylphosphoramide, the engine was stillviolently preigniting. However, at the end of 39 hours only mildpreignition was encountered and at the end of 77 hours no preignitionwas encountered. Even after 101 hours of operation no preignition wasevidenced. However, when the engine was switched back to the referencegasoline, mild preignition was encountered within 22 hours and violentpreignition occurred within The improved results obtained wtih a motorfuel of the invention are thus quite strikingeven'when starting with anengine in which preignition has already been encountered. While ourinvention is described above with reference to various specific examplesand embodiments, it will be understood that the invention is not limitedto such examples and embodiments and may be variously pracfrom 1 to 4carbon atoms.

2. A motor fuel having improved preignition qualities comprising a majoramount of gasoline containing about 1 to about 3 cubic centimeters oftetraethyl lead per gallon of gasoline, a lead scavenging amount of ahalo-hydrocarbon and between about 0.001 and about hydrocarbon andbetween about 0.1 and 1.5 times the theoretical amount ofhexamethylphosphoramide required to convert the lead to lead phosphate.

4. A gasoline preignition improving additive comprising a major amountof tetraethyl lea-d containing a lead scavenging amount of ahalohydrocarbon and an alkyl-phosphoramide in an amount between about0.1 and 1.5 times the theoreticalamount required to convert the I leadto lead phosphate, wherein the alkyl group in said 4.0 percent by weightbased on the gasoline of hexa- 26 methylphosphoramide.

3. A motor fuel having improved preignition qualities comprising a majoramount of gasoline containing about 1 to about 3 cubic centimeters oftetraethyl lead per gallon of gasoline, a lead scavenging amount of ahaloalkyl-phosphoramide contains from 1 to 4 carbon atoms.

5. A gasoline preignition improving additive comprising a major amountoftetraethyl lead containing a lead scavenging amount of ahalohydrocarbon and hexamethylphosphoramide in an amount between about0.1 and 1.5 times the theoretical amount required to convert the lead tolead phosphate.

References Cited in the file of this patent UNITED STATES PATENTSCampbell Aug. 13, 1946 Yust et a1. Oct. 2, 1956 FOREIGN PATENTS GreatBritain Nov. 26, 1952 OTHER REFERENCES Aviation Spark Plug Fouling, ItsCause and Control, by V. E. Yust and E. A. Broegemueller, published bythe Society of Automotive Engineers, Inc., 29 West 39th St., N. Y. 18,N. Y.

1. A MOTOR FUEL HAVING IMPROVED PREIGNITION QUALITIES COMPRISING A MAJORAMOUNT OF GASOLINE CONTAINING ABOUT 1 TO ABOUT 3 CUBIC CENTIMETERS OFTETRAETHYL LEAD PER GALLON OF GASOLINE, A LEAD SCAVENGING AMOUNT OF AHALO-HYDROCARBON AND BETWEEN ABOUT 0.1 AND 1.5 TIMES THE THEORETICALAMOUNT OF AN ALKYL-PHOSPHORAMIDE REQUIRED TO CONVERT THE LEAD TO LEADPHOSPHATE, WHEREIN THE ALKYL GROUP IN SAID ALKYL-PHOSPHORAMIDE CONTAINSFROM 1 TO 4 CARBON ATOMS.